New Gravity Theory Dispenses with Dark Matter

Darkness Matters writes "According to New Scientist, a theory of modified gravity, which has no need of dark matter, has just explained why the Pioneer 10 probe is 400,000 miles off its expected course as it leaves the solar system. It sounds pretty convincing, although in dispensing with dark matter, they've had to utilize the theoretical particle, called a graviton, which appears from the vacuum of space wherever stars are densely packed, making gravity stronger."

Comments

Re:Gravitons are not a new concept

[AKAImBatman]

If a hypothesis involving gravitons is explained by experimental evidence, then this hypothesis could be elevated to theory.

However, we're still left with the age old question: If gravity is manifest as a particle, why can't we shield against it?

Until that question is answered, the graviton theory is going nowhere, fast. :-/

Re:Here we go again

[Dr. Zowie]

and contrary to the eternal "it's just epicycles" cry among Slashdotters, it is testable, falsifiable, and predictive).

Hey, don't run down epicycles! They're testable, falsifiable, and predictive (of future planetary position) -- they're just more weakly predictive, and more complicated, than Newton's laws of gravity. But when Keplerian orbits were invented, those were no more predictive than epicycles. Both are descriptive theories.

Epicycles are actually a valid description of planetary orbits, and are still used today to analyze perturbations in planetary and protoplanetary systems. (A particle in a circular orbit will, if perturbed a small amount, acquire both drift and epicyclic motion relative to its original path).

I still don't buy it

[FhnuZoag]

For those who applaud the end of dark matter, this sort of law-modification theory should really be much more worrying. Dark matter at least has a plausible explanation, is predicted by various theories, makes predictions, and is somewhat intuitive. (come on, how likely is it that all the massive particles in the universe just happen to interact electromagnetically as well? We know from measurements that some, at least, do not - e.g. neutrinos.)

Altering the laws of physics so that they do not behave consistently (specifically, they just happen to do something different when far away from our local experiments) and giving no explanation why this should be so except to fit the previous data is really a terrible way to do things. And if new observations topple your carefully constructed modifications? What are you going to do - change your maths again?

The analogy is seeing a red ball, and declaring not that there is a red ball, but that there is a subtle effect with optics that creates circular red blobs in your vision from time to time.